Basil belonging to the Lamiaceae family, is one of the most important aromatic andmedicinal plants, and is widely cultivated in many countries. Areal parts, especiallyleaves of sweet basil are widely used to enhance the flavour of food stuffs suchas salads, pasta, tomato products, vegetables, pizza, meat, soups, marine foods,confectioneries and other products. In this report, the yield and chemical componentsof essential oils of two species of basil (Ocimum ciliatum and Ocimum basilicum) grown in southwestern of Iran (Chaharmahal and Bakhtiary Province) were investigated. Thewater-distilled oils were analyzed by means of a GC-MS apparatus. The oil yieldsobtained from the aerial parts of Ocimum basilicum were found to be 0.285 mL/100 g and 0.71 mL/100 g when using the dry plant materials, respectively. The major constituents of the essential oil from the aerial parts of O. basilicum were methyl chavicol or estragol (49.7%), linalool (10.7%), α-cadinol (5.9%), (Z)-β-farnesene (3.8%) and 1,8-cineole (3.5%). The main constituents of the essential oil from the aerial parts of O. ciliatum were methyl chavicol (38.1%), (E)-citral (14.6%), (Z)-citral (11.5%), (E)-caryophyllene (6.4%) and cis-α-bisabolene (4.0%). A simple comparison of our results with the previous reports suggests that differences in the essential oil compositions and oil yields of the studied plants could be mainly attributed to genetic diversity in two Iranian species of basil. Manuscript profile